Experimental Studies On Large Sandbag Cofferdam Stability In Deep Soft Soil

Large sandbag cofferdam(dam) is currently in the development of the construction of cofferdam on the soft soil foundation(dam) technology, whether in theory or in practice is not mature, there are a lot of problems need to study, such as stability and large deformation problems. In this thesis, taking a round the sea land building engineering of tianjin big sandbag cofferdam, using the combination of site construction in the process of instability, large sandbag on deep soft foundation cofferdam stability problem of experimental study and numerical simulation analysis.The main study includes: By means of the case study,construction spot observation, data analysis of large sandbag Draw the main achievements as follows:(1) Large sandbag buckling failure mode is the insufficient foundation strength, large settlement of cofferdam, close to the dam body under the central block, foundation slope foot outward horizontal displacement and uplift, slope toe foundation losing stability, sliding down slope, slope middle elevation area geotextile tensile fracture.(2) Under the condition of the foundation with the super soft soil, the driven into the plastic plate and the laying of drainage sand cushion layer can effectively accelerate the foundation drainage consolidation, and it is useful for the cofferdam stability. But, in the case of a drainage channel, the strength of the soft soil growth is still slow., therefore, it must be strictly controlled the upper cofferdam construction progress to make soft soil strength increasing top load to bear, otherwise, it will cause the foundation together with the cofferdam overall sliding failure of slope.(3) The large sandbag geotextile has good coordination deformation effect, and can maintain overall form of settlement of cofferdam with large deformation in foundation and cofferdam, only under the condition of the low strength of foundation soil it may fail to prevent the slope toe of the cofferdam and the slope of the sliding failure.(4) The rheological properties of soft soil is stronger, after the completion of the cofferdam period, there will be dozens of the settlement of cm.(5) Through the test for the measurement method and technology of geotextile strain in the centrifuge, good measurement results have been achieved. The result shows that the middle position of the bottom cofferdam is compressed, but near the surface of the slope,the geotextile shows the tensile deformation condition. and the deformation and the appearance of the cofferdam is consistent, shows that the measured results are more credible.